Liquid crystal displays are commonly used as displays for compact electronic apparatuses. This is because they not only provide good quality images with little power consumption but also because they are very thin. The liquid crystal layer in a liquid crystal display does not emit any light beams itself. The liquid crystal has to be lit by a light source so as to clearly and sharply display text and images. Thus, a backlight module is generally needed for a liquid crystal display.
Referring to FIG. 10, a typical backlight module 10 includes a reflective film 11, a light guide plate 12, a light source 13, and a holding frame (not labeled). The light guide plate 12 includes a light incident surface 121, and a bottom surface (not labeled) perpendicularly adjoining the light incident surface 121. The light source 13 is disposed adjacent to the light incident surface 121, and the reflective film 11 is disposed adjacent to the bottom surface of the light guide plate 12. The holding frame includes a plastic frame 15 and a tray 16, which cooperatively form a space to accommodate the reflective film 11, the light guide plate 12 and the light source 13.
The plastic frame 15 includes a plurality of first side walls 151. A bottom edge of each first side wall 151 includes a plurality of protrusions 152 extending downwardly and then outwardly therefrom. The tray 16 includes a bottom plate 161, and a plurality of second side walls 162 perpendicularly extending up from edges of the bottom plate 161. The tray 16 further defines a plurality of notches 163 at junctions between the bottom plate 161 and the second side walls 162. The notches 163 correspond to the protrusions 152, respectively.
Referring also to FIG. 11, in a process of assembling the backlight module 10, the reflective film 11, the light guide plate 12 and the light source 13 are arranged in the tray 16. Then the plastic frame 15 is aligned with the tray 16 and pushed toward the tray 16. The first side walls 151 of the plastic frame 15 slide along inner surfaces of the second side walls 162 of the tray 16. When the bottom edges of the first side walls 151 reach the edges of the tray 161 of the bottom plate 16, the protrusions 152 are snappingly received in the notches 163 of the tray 16. Thus, the plastic frame 15 is engaged with the tray 16, and the backlight module 10 is fully assembled.
However, in the process of assembling the backlight module 10, the protrusions 152 of the plastic frame 15 are elastically deformed while the first side walls 151 of the plastic frame 15 slide along the inner surfaces of the second side walls 162 of the tray 16. Once the protrusions 152 reach the notches 163, the plastic frame 15 generally has to be manually pressed so that all the protrusions 152 can snappingly engage in the notches 163. Considerable force may be required during such pressing. Therefore, the plastic frame 15 may be distorted or even be damaged. When this occurs, the mechanical stability and the performance of the backlight module 10 are liable to be impaired. Furthermore, a process of disassembling the backlight module 10 can be awkward and difficult.
What is needed, therefore, is a holding frame that can overcome the above-described deficiencies. What is also needed is a backlight module including the holding frame.